U.S. patent application number 11/558271 was filed with the patent office on 2008-05-15 for system and method for joint arthroplasty.
This patent application is currently assigned to Hayes Medical, Inc.. Invention is credited to Michael Guidera, Daniel F. Justin, Chad W. Lewis, Michael A. Serra.
Application Number | 20080114462 11/558271 |
Document ID | / |
Family ID | 39370218 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080114462 |
Kind Code |
A1 |
Guidera; Michael ; et
al. |
May 15, 2008 |
SYSTEM AND METHOD FOR JOINT ARTHROPLASTY
Abstract
An orthopaedic joint prosthesis may include a first component, a
bearing component, and a third component. The first component has a
base and a keel protruding from the base to extend into a first
bone. The keel's longitudinal axis is offset from a geometric
center of the base. The base has a first articular surface and the
bearing component has a second articular surface shaped to
articulate with the first articular surface. A feature unitary with
the first component reversibly attaches to the bearing component.
The bearing component has a third articular surface shaped to
articulate with a fourth articular surface on the third component.
A distraction feature of the bearing component is shaped to provide
alignment and/or distraction between the first articular surface
and the fourth articular surface during insertion of the bearing
component into a joint space between the first and second
bones.
Inventors: |
Guidera; Michael;
(Newcastle, CA) ; Serra; Michael A.; (Cameron
Park, CA) ; Justin; Daniel F.; (Logan, UT) ;
Lewis; Chad W.; (Ogden, UT) |
Correspondence
Address: |
MEDICINELODGE INC.
180 SOUTH 600 WEST
LOGAN
UT
84321
US
|
Assignee: |
Hayes Medical, Inc.
Eldorado Hills
CA
|
Family ID: |
39370218 |
Appl. No.: |
11/558271 |
Filed: |
November 9, 2006 |
Current U.S.
Class: |
623/20.27 ;
623/20.15; 623/20.21 |
Current CPC
Class: |
A61F 2/3868 20130101;
A61F 2/389 20130101; A61F 2002/30616 20130101; A61F 2002/305
20130101; A61F 2002/30383 20130101; A61F 2002/30878 20130101 |
Class at
Publication: |
623/20.27 ;
623/20.15; 623/20.21 |
International
Class: |
A61F 2/38 20060101
A61F002/38 |
Claims
1. An orthopaedic prosthesis comprising: a first component
comprising a base and a keel protruding from the base to extend
into a first bone, the keel having a longitudinal axis
medial-laterally offset from a geometric center of the base, the
base having a first articular surface; and a bearing component
comprising a second articular surface shaped to articulate with the
first articular surface, and a third articular surface shaped to
articulate with a fourth articular surface on a second bone.
2. An orthopaedic prosthesis as recited in claim 1, wherein the
first bone comprises a tibia, the second bone comprises a femur,
and the orthopaedic prosthesis comprises a knee prosthesis, the
first component comprising a tibial component of the knee
prosthesis.
3. An orthopaedic prosthesis as recited in claim 2, further
comprising a femoral prosthesis securable to the femur, the femoral
prosthesis having the fourth articular surface.
4. An orthopaedic prosthesis as recited in claim 1, wherein the
bearing component is constrained to rotate without translation
about a rotation axis relative to the first component.
5. An orthopaedic prosthesis as recited in claim 4, wherein the
rotation axis is offset from a geometric center of the base in at
least one of the medial-lateral direction and anterior-posterior
direction.
6. An orthopaedic prosthesis as recited in claim 1, wherein the
bearing component is constrained to translate without rotation
along one or more of a medial-lateral direction and an
anterior-posterior direction.
7. An orthopaedic prosthesis as recited in claim 1, wherein the
bearing component is constrained to rotate about a rotation axis
and to translate relative to the first component.
8. An orthopaedic prosthesis as recited in claim 7, wherein the
rotation axis is offset from a geometric center of the base in at
least one of the medial-lateral direction and anterior-posterior
direction.
9. An orthopaedic prosthesis as recited in claim 1, further
comprising a unitary snap feature shaped to permit the bearing
component to snap into engagement with the first component to
constrain articulation between the first articular surface and the
second articular surface.
10. An orthopaedic prosthesis as recited in claim 1, wherein one of
the first component and the bearing component comprises a
distraction feature shaped to provide at least one of alignment and
distraction between the first articular surface and the fourth
articular surface during insertion of the bearing component into a
joint space between the first and second bones.
11. An orthopaedic prosthesis comprising: a first component
securable to a first bone, the first component comprising a first
articular surface and a unitary feature; and a bearing component
comprising a second articular surface shaped to articulate with the
first articular surface and a third articular surface shaped to
articulate with a fourth articular surface on a second bone;
wherein the unitary feature is shaped to constrain articulation
between the first articular surface and the second articular
surface.
12. An orthopaedic prosthesis as recited in claim 11, wherein the
first bone comprises a tibia, the second bone comprises a femur,
and the orthopaedic prosthesis comprises a knee prosthesis, the
first component comprising a tibial component of the knee
prosthesis.
13. An orthopaedic prosthesis as recited in claim 12, further
comprising a femoral prosthesis securable to the femur, the femoral
prosthesis having the fourth articular surface.
14. An orthopaedic prosthesis as recited in claim 11, wherein the
bearing component is constrained to rotate without translation
about a rotation axis relative to the first component.
15. An orthopaedic prosthesis as recited in claim 14, wherein the
rotation axis is offset from a geometric center of the base in at
least one of the medial-lateral direction and anterior-posterior
direction.
16. An orthopaedic prosthesis as recited in claim 11, wherein the
bearing component is constrained to translate without rotation
along one or more of a medial-lateral direction and an
anterior-posterior direction.
17. An orthopaedic prosthesis as recited in claim 11, wherein the
bearing component is constrained to rotate about a rotation axis
and to translate relative to the first component.
18. An orthopaedic prosthesis as recited in claim 17, wherein the
rotation axis is offset from a geometric center of the base in at
least one of the medial-lateral direction and anterior-posterior
direction.
19. An orthopaedic prosthesis as recited in claim 11, further
comprising a unitary snap feature shaped to permit the bearing
component to snap into engagement with the first component to
constrain articulation between the first articular surface and the
second articular surface.
20. An orthopaedic prosthesis as recited in claim 11, wherein one
of the first component and the bearing component comprises a
distraction feature shaped to provide at least one of alignment and
distraction between the first articular surface and the fourth
articular surface during insertion of the bearing component into a
joint space between the first and second bones.
21. An orthopaedic prosthesis comprising: a first component
securable to the first bone, the first component comprising a first
articular surface; and a bearing component comprising a second
articular surface shaped to articulate with the first articular
surface and a third articular surface shaped to articulate with a
fourth articular surface on a second bone; wherein one of the first
component and the bearing component comprises a distraction feature
shaped to provide at least one of alignment and distraction between
the first articular surface and the fourth articular surface during
insertion of the bearing component into a joint space between the
first and second bones.
22. An orthopaedic prosthesis as recited in claim 21, wherein the
first bone comprises a tibia, the second bone comprises a femur,
and the orthopaedic prosthesis comprises a knee prosthesis, the
first component comprising a tibial component of the knee
prosthesis.
23. An orthopaedic prosthesis as recited in claim 22, further
comprising a femoral prosthesis securable to the femur, the femoral
prosthesis having the fourth articular surface.
24. An orthopaedic prosthesis as recited in claim 21, wherein the
bearing component is constrained to rotate without translation
about a rotation axis relative to the first component.
25. An orthopaedic prosthesis as recited in claim 24, wherein the
rotation axis is offset from a geometric center of the base in at
least one of the medial-lateral direction and anterior-posterior
direction.
26. An orthopaedic prosthesis as recited in claim 21, wherein the
bearing component is constrained to translate without rotation
along one or more of a medial-lateral direction and an
anterior-posterior direction.
27. An orthopaedic prosthesis as recited in claim 21, wherein the
bearing component is constrained to rotate about a rotation axis
and to translate relative to the first component.
28. An orthopaedic prosthesis as recited in claim 27, wherein the
rotation axis is offset from a geometric center of the base in at
least one of the medial-lateral direction and anterior-posterior
direction.
29. An orthopaedic prosthesis as recited in claim 21, further
comprising a unitary snap feature shaped to permit the bearing
component to snap into engagement with the first component to
constrain articulation between the first articular surface and the
second articular surface.
30. A method of implanting an orthopaedic prosthesis, the method
comprising: anchoring a base of the first component to the first
bone by inserting keel of the first component into the first bone,
the keel having a longitudinal axis medial-laterally offset from a
centroid of the base; and coupling a bearing component to the first
component such that a second articular surface of the bearing
component articulates with a first articular surface of the base
and a third articular surface of the bearing component is
positioned to articulate with a fourth articular surface on a
second bone.
31. A method as recited in claim 30, wherein the first bone
comprises a tibia, the second bone comprises a femur, and the
orthopaedic prosthesis comprises a knee prosthesis, the first
component comprising a tibial component of the knee prosthesis.
32. A method as recited in claim 31, further comprising securing a
femoral prosthesis to the femur, the femoral prosthesis having the
fourth articular surface.
33. A method as recited in claim 30, wherein coupling the bearing
component to the first component comprises constraining the bearing
component to rotate without translation about a rotation axis
relative to the first component.
34. A method as recited in claim 30, wherein the rotation axis is
offset from a geometric center of the base in at least one of the
medial-lateral direction and anterior-posterior direction.
35. A method as recited in claim 34, wherein coupling the bearing
component to the first component comprises constraining the bearing
component to translate without rotation along one or more of a
medial-lateral direction and an anterior-posterior direction.
36. A method as recited in claim 30, wherein coupling the bearing
component to the first component comprises constraining the bearing
component to rotate about a rotation axis and to translate relative
to the first component.
37. A method as recited in claim 30, wherein the rotation axis is
offset from a geometric center of the base in at least one of the
medial-lateral direction and anterior-posterior direction.
38. A method as recited in claim 30, wherein coupling the bearing
component to the first component comprises reversibly snapping a
unitary snap feature of the first component into engagement with
the first component to constrain articulation between the first
articular surface and the second articular surface.
39. A method as recited in claim 30, further comprising inserting
the bearing component into a joint space between the first and
second bones, wherein inserting the bearing component into the
joint space comprises providing at least one of alignment and
distraction between the first articular surface and the fourth
articular surface with a distraction feature of one of the first
component and the bearing component.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The following disclosure is incorporated herein by
reference:
[0002] U.S. application Ser. No. 07/940,441, filed Sep. 4, 1992,
now U.S. Pat. No. 5,271,737, which is entitled TIBIAL PROSTHETIC
IMPLANT WITH OFFSET STEM.
BACKGROUND OF THE INVENTION
[0003] 1. The Field of the Invention
[0004] The present invention relates generally to orthopaedic
medicine, and more particularly, to knee arthroplasty.
[0005] 2. The Relevant Technology
[0006] Current orthopaedic prostheses have many problems, including
incompatibility with mating prepared bone surfaces, the inevitable
wear of the prosthesis, and inability to mimic the native joint
biomechanics. Fixed-bearing knee prostheses (e.g., the meniscal
prosthesis is fixed relative to the tibial prosthesis) have been
shown to have greater wear rates compared to mobile-bearing
prosthesis (e.g., the meniscal prosthesis is movable relative to
the tibial prosthesis). In addition, mobile-bearing prostheses are
likely to mimic native joint biomechanics more closely than
fixed-bearing prostheses. Known mobile-bearing knee prosthesis
components typically are not fully optimized to maximize bone
purchase and fixation, while minimizing native tissue damage or
resection.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Various embodiments of the present invention will now be
discussed with reference to the appended drawings. It is
appreciated that these drawings depict only typical embodiments of
the invention and are therefore not to be considered limiting of
its scope.
[0008] FIG. 1 is a perspective view of a mobile bearing knee
prosthesis according to one embodiment of the invention.
[0009] FIG. 2 is a perspective view of a first component of the
mobile bearing knee prosthesis of FIG. 1.
[0010] FIG. 3 is a perspective view of the first component of FIG.
2.
[0011] FIG. 4 is a perspective view of a bearing component of the
mobile bearing knee prosthesis of FIG. 1.
[0012] FIG. 5 is a perspective view of the bearing component of
FIG. 4.
[0013] FIG. 6 is a perspective view of a third component of the
mobile bearing knee prosthesis of FIG. 1.
[0014] FIG. 7 is a sagittal cross-section view of the mobile
bearing knee prosthesis of FIG. 1.
[0015] FIG. 8 is a sagittal cross-section view of the mobile
bearing knee prosthesis of FIG. 1 illustrating an alternative
embodiment of the bearing component.
[0016] FIG. 9 is an enlarged sagittal cross-section view of the
mobile bearing knee prosthesis of FIG. 8 illustrating the unitary
feature.
[0017] FIG. 10 is a perspective view of a bearing component
according to one alternative embodiment of the invention, which may
be used in place of the bearing component of FIG. 4 to provide
relative translation as well as rotation between the bearing
component and the first component.
[0018] FIG. 11 is a perspective view of a first component according
to one alternative embodiment of the invention, which may be used
in place of the first component of FIG. 2 to provide a rotation
axis offset in the anterior-posterior direction from the geometric
center of the first component.
[0019] FIG. 12 is a perspective view of a first component according
to one alternative embodiment of the invention, which may be used
in place of the first component of FIG. 2 to provide a rotation
axis offset in the anterior-posterior and medial-lateral direction
from the geometric center of the first component.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The present invention relates to orthopaedic medicine, and
in particular, to total knee arthroplasty. Those of skill in the
art will recognize that the systems and methods described herein
may be readily adapted for any total joint arthroplasty
procedure.
[0021] Referring to FIG. 1, an antero-lateral perspective view
illustrates a mobile bearing knee prosthesis 50 according to one
embodiment of the invention, implanted in a knee. This figure and
subsequent figures may be oriented according to the reference arrow
diagram 10, having a proximal direction 12, a distal direction 14,
an anterior direction 16, a posterior direction 18, and a
medial/lateral axis 20. In this application, "left" and "right" are
used with reference to a posterior view. "Medial" refers to a
position or orientation toward a sagittal plane (i.e., plane of
symmetry that separates left and right sides of the body from each
other), and "lateral" refers to a position or orientation
relatively further from the sagittal plane.
[0022] The prosthesis 50 has three components: a first component
100, a bearing component 200, and a third component 300. In this
embodiment of the invention, the first component 100 is a tibial
tray, which is implanted into a prepared proximal end of a first
bone 22, in this example a tibia. The third component 300 is
implanted into a prepared distal end of a second bone 24, in this
example a femur. The bearing component 200 is attached onto the
first component 100, and provides a bearing surface which maximizes
contact with both the first component 100 and the third component
300.
[0023] Referring to FIG. 2, a perspective view illustrates the
first component 100. The keel offset illustrated in this and other
figures may be similar to that invented by Baldwin, et al. in U.S.
Pat. No. 5,271,737, which patent is hereby incorporated herein by
reference. The first component 100 may comprise cobalt, chrome,
molybdenum, titanium, polymers, mixtures thereof, or any other
materials that are known to be useful implant materials in the
orthopaedic arts. The first component 100 comprises a
non-symmetrical ovoid plate 102 with a flat bearing-facing side 104
and a bone-facing side 106. The bearing-facing side 104 has a first
articulating surface 105 which articulates with the bearing insert
200.
[0024] Extending distally from the bone-facing side 106 is a keel
108, by which the first component 100 is affixed to the prepared
bone. In this embodiment of the invention, the keel 108 is offset,
in both the anterior-posterior and medial-lateral directions, from
the center of the bone-facing side 106 so that it does not extend
into the cortical material of the bone. Also extending distally
from the bone-facing side 106 is a plurality of pegs 110, which
will be more clearly illustrated subsequently.
[0025] Protruding from the bearing-facing side 104 is a unitary
columnar post 112. The post 112 is generally centered on the
bearing-facing side 104, but it can also be offset along the
anterior, posterior, and/or medial-lateral directions 16, 18, 20 to
correspond to the joint's longitudinal rotation axis. The post 112
protrudes from the bearing-facing side 104 to a variable length
which is long enough to retain the bearing component 200, and
terminates at a proximal end 114.
[0026] Near the proximal end 114 is an annular groove 116 which is
narrower in diameter than the remainder of the post 112.
Immediately above the annular groove 116 is an annular ridge 118,
whose diameter is wider than that of the groove 116 and the
remainder of the post 112. The annular groove 116 and annular ridge
118 form part of a unitary snap feature which securely and
reversibly attaches the bearing component 200 to the first
component 100 while simultaneously allowing the bearing component
200 some freedom to rotate relative to the first component 100. In
other embodiments, the bearing component may translate or translate
and rotate relative to the first component. One such embodiment
will be shown and described subsequently, in connection with FIGS.
10, 11, and 12.
[0027] Referring to FIG. 3, a perspective view illustrates the
bone-facing side 106 of the first component 100. The bone-facing
side 106 has a bone-facing surface 120. The bone-facing surface
120, keel 108 and pegs 110 may comprise a porous material that
encourages bone ingrowth. A notch 122 is indented into a posterior
side 124 of the plate 102 in this embodiment, to allow room for
retainment of the posterior cruciate ligament (PCL) or another
ligament behind the plate 102.
[0028] In other embodiments of the invention, the first component
100 can vary according to the joint being replaced or the specific
anatomy of the patient. For example, the dimensions and surface
area of the plate 102 can vary, as can the size and placement of
the keel 108, and the height, diameter and placement of the post
112. The pegs 110 may be present or absent. The notch 122 may vary
in size, shape, and placement, or be absent as in the case of a PCL
sacrificing insert.
[0029] Referring to FIG. 4, a perspective view of the bearing
component 200 is shown. The bearing component 200 has a first
component facing side 202 with a second articulating surface 203
and a third component facing side 204 with a third articulating
surface 205, which is divided into medial and lateral portions. It
has an anterior end 206, a posterior end 208, a medial end 210 and
a lateral end 212. The third articulating surface 205 is sculpted
and curved to align with the third component 300 when the
prosthesis 50 is implanted in the patient. In the event that a
hemiarthroplasty, rather than a full arthroplasty, is desired, the
third articulating surface 205 may instead articulate with the
natural distal end of the femur.
[0030] A bore 214 is generally centrally located, extending through
the bearing component 200 from the first component facing side 202
to the third component facing side 204. The bore 214 is positioned
to fit over the post 112 of the first component, allowing the flat
first component facing side 202 to align with the flat bearing
facing side 104 when the bearing component 200 is reversibly
attached to the first component 100. Immediately adjacent to where
the bore 214 opens to the third component facing side 204, the
diameter of the bore 214 is greater, forming a circular groove 216.
Just below the groove 216 in a distal direction is a circular rim
218, where the diameter of the bore 214 is wider than in the groove
216. The bearing component rim 218 reversibly retains the bearing
component 200 relative to the first component 100 because the
annular ridge 118 seats against the shoulder defined by the rim
218.
[0031] In the embodiment illustrated, a height of the anterior end
206 is higher than a height of the posterior end 208. This
configuration allows increased anterior stability with the third
component 300. An alternate bearing component configuration (not
shown), in which the heights of the anterior 206 and posterior 208
ends are closer to equal, provides equal stability, between the
anterior and posterior ends of the bearing component 200.
[0032] Referring to FIG. 5, a perspective view of the bearing
component 200 is shown. Where the first component facing side 202
meets the anterior end 206, an instrument slot 220 is formed as a
depression in the second articulating surface 203. The instrument
slot 220 allows insertion of a wedge instrument (not shown) to pry
the bearing component 200 from the first component 100. A channel
222, which is a groove indented into the second articulating
surface 203, extends from the bore 214 to generally the posterior
end 208. The channel 222 may be ramped such that the depth of the
channel varies between the posterior end 208 and the bore 214. The
channel configuration allows the bearing component 200 to
self-align as it is slid in an anterior to posterior direction into
place over the post 112, with a minimum of distraction of the
joint. In addition, the channel configuration allows the bearing
component to be more easily removed during bearing replacement,
with minimum joint distraction.
[0033] Near the posterior end of the channel 222, a cutout 224
abuts the channel 222 on both sides. The cutout 224 is a depression
in the second articulating surface 203 along the posterior end 208
extending from both sides of the channel 222 along the
medial-lateral axis. The cutout 224 may be shallower than, or as
deep as, the channel 222, and may or may not include a notch for
the PCL. The purpose of the cutout 224 is to prevent creep of the
bearing insert material over time by distributing the stress on the
insert 200 to where it is in surface contact with the first
component 100.
[0034] The bearing component 200 may be formed of ultra-high
molecular weight polyethylene (UHMWPE), but may, in alternative
embodiments, comprise a different polymer, a cross linked polymer,
or an interpenetrating polymer network (e.g., comprising of
hyaluronic acid), or an HIP processed polymer material.
Alternatively, the bearing component 200 may comprise a combination
of metallic and non-metallic materials, such as a metal base with a
polymer top.
[0035] Referring to FIG. 6, a perspective view of the third
component 300 is shown. In this embodiment of the invention, a
femoral component is depicted, but in other embodiments, the third
component 300 may be a femoral component, a natural knee, or a bone
of another joint. The third component 300 has a curved V shape,
with a trochlear groove 302 adjoining two condyles 304 extending
posteriorly and then curving cephalically, to match the contours of
a natural distal end of a femur. The trochlear groove 302 and
condyles 304 have a bone-facing side 306, and a bearing-facing side
308 which has a fourth articulating surface 3 10. The radius of the
curvature of the condyles 304 relatively matches the contours of
the third articulating surface 205 on the bearing component
200.
[0036] Extending proximally from the bone-facing side 306 of each
condyle 304 is a stem 312, which is configured to be driven into a
prepared second bone, or a femur in this embodiment. The
bone-facing side 306 has a bone-facing surface 314 which may
comprise a porous material to encourage bone ingrowth. A gap 316
between the condyles 304 is generally a fixed height, but the
condyles 304 may be of various widths, sizes and curvatures
depending on the specific anatomy of the patient or bearing
component 200. The surface curvature of the condyles 304 may also
vary to match the curvature of the specific bearing component 200
chosen for the patient's mobility requirements.
[0037] Referring to FIGS. 7, a sagittal cross-section of the
prosthesis 50 is shown. During the implantation procedure, the
first component 100 may first be implanted in the first bone. Next,
the bearing component 200 is reversibly attached onto the first
component 100 and lastly the third component 300 is implanted in
the second bone, which may be a femur. Alternatively, the order of
implantation of the last two components (the bearing component 200
and the third component 300) may be reversed.
[0038] When the bearing component 200 is snapped into engagement
(i.e., reversibly attached) with the first component 100, it is
slid in an anterior to posterior direction with the channel 222
sliding over the proximal end 114 of the post 112, until the bore
214 slips over the post 112. The bore 214 slides down the post 112
until resistance is encountered as the rim 218 meets the ridge 118.
The bearing component 200 is pushed until the rim 218 deforms and
snaps past the ridge 118, and the rim 218 rests in the annular
groove 116 of the post 112 while the ridge 118 rests in the groove
216 of the bore 214. Thus reversibly attached together, the bearing
component 200 remains engaged with the first component 100 until
pried apart by the wedge tool (not shown). However, the engagement
is loose enough to allow movement of the bearing component 200
relative to the first component 100. Movement between the bearing
component 200 and the first component 100 allows the bearing
component 200 to more readily align with the third component 300.
This provides increased area contact, and reduced point contact,
thereby reducing wear and other mechanical failure between the
bearing component 200 and the third component 300.
[0039] Referring to FIG. 8, a sagittal cross-section illustrates a
prosthesis 450 according to an alternative embodiment of the
invention. The prosthesis 450 is similar to the prosthesis 50
described previously, except that the prosthesis 450 has a bearing
component 500 with a configuration different from that of the
bearing component 200. More precisely, a channel 522, which is a
groove indented into the second articulating surface 203, extends
from the bore 214 to generally the posterior end 208 of the bearing
component 500. The channel 522 is ramped such that the depth of the
channel 522 varies between the posterior end 208 and the bore
214.
[0040] The ramped shape of the channel 522 helps to provide
alignment and/or distraction between the first and fourth
articulating surfaces 105, 310 during insertion of the bearing
component 500 into a joint space between the first and second
bones. The configuration of the channel 522 allows the bearing
component 500 to self-align as it is slid in an anterior to
posterior direction into place over the post 112, with a minimum of
distraction of the joint. In addition, the configuration of the
channel 522 allows the bearing component 500 to be more easily
removed during bearing replacement, with minimum joint
distraction.
[0041] Referring to FIG. 9, an enlarged sagittal cross-sectional
view illustrates a portion of the prosthesis 450, in particular the
reversible attachment mechanism between first component 100 and
bearing component 500. As the bearing component 500 is reversibly
attached to the first component 100, it is slid in an anterior to
posterior direction with the channel 222 sliding over the proximal
end 114 of the post 112, until the bore 214 slips over the post
112. The bore 214 slides down the post 112 until resistance is
encountered as the rim 218 meets the ridge 118. The bearing
component 200 is pushed until the rim 218 deforms and deforms past
the ridge 118, and the rim 218 rests in the annular groove 116 of
the post 112 while the ridge 118 rests in the groove 216 of the
bore 214. Thus reversibly attached together, the bearing component
500 remains engaged with the first component 100.
[0042] Referring to FIG. 10, a perspective view illustrates a
bearing component 400 according to an alternative embodiment of the
invention. A bore 414 is generally centrally located, extending
through the bearing component 200 from the first component facing
side 202 to the third component facing side 204. In the embodiment
shown, the bore 414 has an elongated shape, thus allowing
translation along with rotation. The elongated shape can either be
generally parallel to the medial-lateral axis 20, as shown in FIG.
10, or parallel to anterior and posterior directions 16 and 18,
allowing translation and rotation along the major axis of the
bearing component 400 relative to the first component 100. In
alternative embodiments (not shown), a bore may be shaped to permit
both anterior-posterior, and medial-lateral, relative motion
between a bearing component and the associated first component.
Such embodiments may or may not permit relative rotation between
the bearing component and the first component.
[0043] The bore 414 is positioned to fit over the post 112 of the
first component, allowing the flat first component facing side 202
to align with the flat bearing facing side 104 when the bearing
component 400 is snapped into engagement (i.e., reversibly
attached) with the first component 100. Immediately adjacent to
where the bore 414 opens to the third component facing side 204,
the diameter of the bore 414 is greater, forming a groove 416. Just
below the groove 416 in a distal direction is a rim 418, where the
diameter of the bore 414 is wider than in the groove 416. The
groove 416 and the rim 418 facilitate retention of the bearing
component 400 relative to the first component 100 in a manner
similar to that of their counterparts 216, 218 of the bearing
component 200 of the previous embodiment.
[0044] Referring to FIG. 11, a perspective view illustrates a first
component 500 according to an alternative embodiment of the
invention. The first component 500 comprises an asymmetrical ovoid
plate 102 with a flat bearing-facing side 104 and a bone-facing
side 106. The bearing-facing side 104 has a first articulating
surface 105 which articulates with the bearing insert 200.
Extending distally from the bone-facing side 106 is a keel 108, by
which the first component 100 is affixed to the prepared bone. In
this embodiment of the invention, the keel 108 is offset, in both
the anterior-posterior and medial-lateral directions, from the
center of the bone-facing side 106 so that it does not extend into
the cortical material of the bone. Also extending distally from the
bone-facing side 106 is a plurality of pegs 110.
[0045] Protruding from the bearing-facing side 104 is a unitary
columnar post 512. The post 512 is offset anteriorly to optimize
biomechanics such that the anterior distance 502 is less than the
posterior distance 501. The post 512 protrudes from the
bearing-facing side 104 to a length which is sufficient to retain
the bearing component 200, and terminates at a proximal end 514.
The unitary columnar post 512 and proximal end 514 constrains
movement of the bearing component 200 relative to the first
component 500 in a manner similar to that of their counterparts 512
and 514 of the first component 100 of the previous embodiment.
[0046] Referring to FIG. 12, a perspective view illustrates a first
component 600, according to an alternative embodiment of the
invention. The first component 500 comprises a non-symmetrical
ovoid plate 102 with a flat bearing-facing side 104 and a
bone-facing side 106. The bearing-facing side 104 has a first
articulating surface 105 which articulates with the bearing insert
200. Extending distally from the bone-facing side 106 is a keel
108, by which the first component 100 is affixed to the prepared
bone. In this embodiment of the invention, the keel 108 is offset,
in both the anterior-posterior and medial-lateral directions, from
the center of the bone-facing side 106 so that it does not extend
into the cortical material of the bone. Also extending distally
from the bone-facing side 106 is a plurality of pegs 110.
[0047] Protruding from the bearing-facing side 104 is a unitary
columnar post 612. The post 612 is offset both anteriorly and
medial-laterally to optimize biomechanics such that, in addition to
the anterior offset illustrated in FIG. 11, the medial distance 602
is larger than lateral distance 601. An alternative embodiment (not
shown) includes a post offset only in the medial-lateral direction
20. The post 612 protrudes from the bearing-facing side 104 to a
length which is sufficient to retain the bearing component 200, and
terminates at a proximal end 614. The unitary columnar post 612 and
proximal end 614 constrains movement of the bearing component 200
relative to the first component 600 in a manner similar to that of
their counterparts 612 and 614 of the first component 100 of the
previous embodiment.
[0048] In alternative embodiments, the various components shown and
described herein may have different sizes, configurations (such as
placement of the keel and post, the width of condyles, and the
like) material properties, and other variations to adapt them to
variations in patient anatomy. If desired, multiple versions of
each of the first, second, and bearing components may be provided
together in a single kit to enable a surgeon to interoperatively
select the best set of components for a patient.
[0049] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. It is appreciated that various features of the
above-described examples can be mixed and matched to form a variety
of other alternatives. As such, the described embodiments are to be
considered in all respects only as illustrative and not
restrictive. The scope of the invention is, therefore, indicated by
the appended claims rather than by the foregoing description. All
changes which come within the meaning and range of equivalency of
the claims are to be embraced within their scope.
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